It's not that he's casual about what happened to him, more that he seems resigned over it, that he's chosen to not be overly emotional. Not hiding his past, not being ashamed of it, as evidenced by him telling a nearly complete stranger. Acceptance at the very least, apathy at the worst.

"I do, or at least I can imagine the feeling as it seems similar to certain aspects of being what I am. That doesn't mean it wasn't horrible for you as an individual and if you need to talk about it, I don't mind listening."